The invention relates to a method and to an apparatus for acquisition of multistandard video data.
Existing video data slicers are capable of digitizing incoming signals of different video systems and data services. They provide serial digital data and a clock signal for synchronous data transfer. This data has to be searched for valid start codes of a specific service or of several services in parallel.
Conventional video data acquisition circuits only search the serial data stream for the occurance of specific start codes related to a single service. The xe2x80x9cintegrated video input processorsxe2x80x9d (SAA5281 by Philips) for more than one service is restricted to a specific video system (625 lines) and uses different single-standard acquisition circuits in parallel.
It is an object of the invention to disclose a method for the acquisition of multistandard video data. This object is achieved by the method disclosed in claim 1.
It is a further object of the invention to disclose an apparatus which utilises the inventive method. This object is achieved by the apparatus disclosed in claim 8.
Advantageous additional embodiments of the inventive method and apparatus are disclosed in the respective dependent claims.
According to the invention for acquisition of multistandard video data an incoming data stream is loaded into a first memory and a parallel search for different start codes on the same data containing for different services different framing codes is performed, when service in actual video line is not specified and those start codes looked for are changeable by configuration.
The decoder is controlled by a microprocessor. Advantageously the decoder can be enabled or disabled by the microprocessor via an enable signal.
The clock frequency of the decoder is adapted to the frequency of the different start codes.
Further, a service selection block determines what kind of framing code is looked for based on the line number of a given input signal, the used standard of that input signal and the availability of a certain code in a specific line of that input signal.
Advantageously within an active interval of a service specific timing signal, generated by a search window generator from a horizontal synchron signal, up to 3 bytes are scanned for the appropriate framing code.
In principle 3 bytes are dedicated to the framing code of a line containing a first WSS signal that contains 24 elements based on 5 MHz. In the case of a line containing a second VPS signal, only 2 bytes are compared to the start code consisting of the two bytes based on 5 MHz. In the case of a line containing a third signal like Close Caption only 1 byte is simultaneously compared to both start codes based on 1007 kHz. In the case of a line containing a fourth WST signal, again only one byte has to be compared to the framing code based on 6.9375 MHz, and when the start code is detected during the active search window, the activated signal starts the data transmission to the buffer which is managed by an output control block.
In the case of a line containing the second VPS signal beside the activated signal another signal is exported to a microprocessor register to indicate the reception of that data in a certain line.
In the case of a line containing the fourth WST signal, the two byte following the framing code of that fourth WST signal are decoded during the search and the result is loaded in parallel to a second memory and when the framing code of that fourth WST signal is detected, the data are transferred to the buffer through this memory.
In principle the inventive apparatus for acquisition of multistandard video data includes:
means for providing start codes;
means for storing incoming data stream;
means for comparing said start codes with said incoming data streams.
Further the apparatus may include additionally means for decoding and storing said incoming data stream.
The application of the digital acquisition implemented here is, of course, not only limited to the acquisition of data services in video signals. It can also be used in any other product of digital signal transmission or processing, where different data services occupy time intervals on a shared transmission channel and may occur deterministically or non-deterministically.